PC DOWNLOAD INSTRUCTIONS
Right-click on the image and choose "Set As Wallpaper"
 
MAC OS 10.5 and higher INSTRUCTIONS

Control-click and select "Use Image as Desktop Picture"

MAC OSX DOWNLOAD INSTRUCTIONS
1. Control-click and select "Download Image to Disk"
2. Save image to Desktop
3. Go to Apple Menu > System Preferences > Personal section and select "Desktop"
4. On the "Collection" pull down menu, go to "Choose Folder" and locate the appropriate wallpaper